Engine control apparatus

Abstract

An apparatus for controlling a spark ignited internal combustion engine comprising a control unit including a memory having first and second tables containing the desired relationships between the engine condition and the spark timing for the engine operating on low and high octane fuels. The control unit calculates a value corresponding to a setting of the spark timing repetitively at uniform intervals from the first table in response to a first level of the control signal and from the second table in response to a second level of the control signal and advances the spark timing at a predetermined rate in the presence of the first level of the control signal and changes to the second level when the spark timing is advanced over a first reference value. The control unit retards the spark timing at a second predetermined rate in response to engine knock in the presence of the second level of the control signal and changes the control signal to the first level when the spark timing is retarded over a second reference value. The control unit stores a maximum advance value β max to which the spark timing is advanced before the spark timing is advanced at the first predetermined rate during the successive advance control. The control unit clears the maximum advance value β max to zero when the spark timing is advanced over the first reference value during the advance control.

What is claimed is: 
     
       1. An apparatus for controlling an internal combusiton engine of the spark ignition type including spark-timing control means for controlling the timing of sparks supplied to the engine, comprising: sensor means for sensing a condition of the engine;   a knock sensor for sensing engine knock;   a control unit including memory means having a first table describing a desired relationship between the sensed engine condition and the spark-timing control means for the engine being operating on first fuel having a first octane number and a second table describing a desired relationship between the sensed engine condition and the spark-timing control means for the engine being operating on second fuel having a second octane number greater than the first octane number, the control unit including means for providing a control signal having a first and second level, and means for calculating a first value corresponding to a setting of the spark-timing control means repetitively at uniform intervals from the first table in response to the first level of the control signal and from the second table in response to the second level of the control signal;   an electrical circuit coupled between the control unit and the spark-timing control means for converting the calculated first value into a setting of the spark-timing control means,;   the control unit including means for performing advance control to advance the spark timing at a first predetermined rate when the sensed engine condition is within a specified range in the presence of the first level of the control signal, and means for changing the control signal from the first level to the second level when the spark timing is advanced over a first reference value during the advance control;   the control unit including means for performing knock control to retard the spark timing at a second predetermined rate in response to the sensed engine knock in the presence of the second level of the control signal, means for changing the control signal from the second level to the first level when the spark timing is retarded over a second reference value less than the first reference value during the knock control;   the control unit including means for storing a maximum value βmax to which the spark timing is advanced at maximum during the advance control, means for advancing the spark timing by the stored maximum value βmax before the spark timing is advanced at the first predetermined rate during the following advance control, and means for clearing the maximum value βmax to zero when the spark timing is advanced over the first reference value during the advance control.   
     
     
       2. The apparatus as claimed in claim 1, wherein the engine includes supercharging control means for controlling the degree of supercharging of the engine, wherein the memory means having a third table describing a desired relationship between the sensed engine condition and the supercharging control means for the engine being operating on the first fuel and a second table describing a desired relationship between the sensed engine condition and the supercharging control means for the engine being operating on the second fuel, wherein the control unit includes means for calculating a second value corresponding to a setting of the supercharging control means from the third table in response to the first level of the control signal and from the fourth table in response to the second level of the control signal, and wherein the apparatus includes an electrical circuit coupled between the control unit and the supercharging control means for converting the calculated second value into a setting of the supercharging control means. 
     
     
       3. The apparatus as claimed in claim 2, wherein the engine includes fuel control means for controlling the amount of fuel supplied to the engine, wherein the memory means having a fifth table describing a desired relationship between the sensed engine condition and the fuel control means for the engine being operating on the first fuel and a sixth table describing a desired relationship between the sensed engine condition and the fuel control means for the engine being operating on the second fuel, wherein the control unit includes means for calculating a third value corresponding to a setting of the fuel control means from the fifth table in response to the first level of the control signal and from the sixth table in response to the second level of the control signal, and wherein the apparatus includes an electrical circuit coupled between the control unit and the fuel control means for converting the calculated third value into a setting of the fuel control means. 
     
     
       4. The apparatus as claimed in claim 1, wherein the engine includes fuel control means for controlling the amount of fuel supplied to the engine, wherein the memory means having a fifth table describing a desired relationship between the sensed engine condition and the fuel control means for the engine being operating on the first fuel and a sixth table describing a desired relationship between the sensed engine condition and the fuel control means for the engine being operating on the second fuel, wherein the control unit includes means for calculating a third value corresponding to a setting of the fuel control means from the fifth table in response to the first level of the control signal and from the sixth table in response to the second level of the control signal, and wherein the apparatus includes an electrical circuit coupled between the control unit and the fuel control means for converting the calculated third value into a setting of the fuel control means.